1. Field of the Invention
The present invention generally relates to a resonance circuit for use in an H-bridge DC-DC converter and, more particularly, to a resonance circuit for use in an H-bridge DC-DC converter capable of converting DC power from the renewable energy or distributed energy into AC power using a DC-DC converter and a DC-AC inverter so as to be fed into the AC utility power system. In the present invention, the resonance circuit for use in an H-bridge DC-DC converter comprises a first resonance circuit, disposed on a buck side of the H-bridge converter, capable of storing the energy in a passive capacitor when any of the active elements is switched and delivering the energy back to the input of the DC-DC converter using a resonance inductor; and a second resonance circuit, disposed on a boost side of the H-bridge converter, for reducing the turn-on loss of a second active switching element to achieve zero-voltage switching. Therefore, the resonance circuit of the present invention is characterized in that a resonance inductor is used to deliver the energy stored in the capacitor back to the input so as to reduce the switching loss and enhance the power conversion rate.
2. Description of the Prior Art
The H-Bridge DC-DC converter converts unstable DC distributed power and renewable power into stable DC power and then the DC-AC inverter inverts the DC power into AC power to be used with the AC utility.
Such an H-bridge DC-DC converter exhibits a wide operation range (Vinmax/Vinmin) so that there is flexibility in circuit design. However, switching loss such as turn-on loss and turn-off loss may result from hard-switching since active switching elements are used. Moreover, during hard-switching of the switches, switching surge occurs to shorten the lifetime of the switching elements.
Therefore, there is need in providing a resonance circuit for use in an H-bridge DC-DC converter to reduce the switching loss, improve the conversion rate and prolong the lifetime of the switching elements.